• Title/Summary/Keyword: microLED

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Effect of Alloying Elements (Cu, Al, Si) on the Electrochemical Corrosion Behaviors of TWIP Steel in a 3.5 % NaCl Solution (3.5% NaCl 수용액 내 TWIP강의 부식거동에 미치는 합금원소 (Cu, Al, Si)의 영향)

  • Kim, Si-On;Hwang, Joong-Ki;Kim, Sung Jin
    • Corrosion Science and Technology
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    • v.18 no.6
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    • pp.300-311
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    • 2019
  • The corrosion behaviors of twinning-induced plasticity (TWIP) steels with different alloying elements (Cu, Al, Si) in a neutral aqueous environment were investigated in terms of the characteristics of the corrosion products formed on the steel surface. The corrosion behavior was evaluated by measuring potentiodynamic polarization test and electrochemical impedance spectroscopy. For compositional analysis of the corrosion products formed on the steel surface, an electron probe x-ray micro analyzer was also utilized. This study showed that the addition of Cu to the steel contributed to the increase in corrosion resistance to a certain extent by the presence of metallic Cu in discontinuous form at the oxide/steel interface. Compared to the case of steel with Cu, the Al-bearing specimen exhibited much higher polarization resistance and lower corrosion current by the formation of a thin Al-enriched oxide layer. On the other hand, Si addition (3.0 wt%) to the steel led to an increase in grain size, which was twice as large as that of the other specimens, resulting in a deterioration of the corrosion resistance. This was closely associated with the localized corrosion attacks along the grain boundaries by the formation of a galvanic couple with a large cathode-small anode.

Empirical Analysis of the Back and Forth Relationship Between China and U.S since 1989: focusing on the Jiangzemin and Clinton's cognitive map (1989년 이후 이중적 중미관계: 장저민과 클린턴의 인지지도 분석을 중심으로)

  • Chung, Da Hoon
    • Korean System Dynamics Review
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    • v.13 no.3
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    • pp.47-66
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    • 2012
  • This paper aims at investigating and identifying the factor that has led the back and forth relationship between China and the United States since 1989. Previous studies on this subject addressed the issue by taking either of two approaches: one with the micro view that interprets the back and forth relationship in the context of the end of the Cold war, on other hand, with the macro view that interprets the fragile relationship in the context of the rise of China. However, neither of the approaches explains with sufficiency the question at hand. Hence for the inquiry, this article suggests a fresh view by exploring alternative method of using a cognitive map of each nation's leader, Jiangzemin and Bill Clinton. This article provides an empirical analysis through the Selected works of Jiangzemin and the speeches of Bill Clinton in 1998 for the first time in the field of Sino-US relationship studies in Korea. With the results of the cognitive map analysis, we can reach the following four points. Firstly, indicators of the forth relationship between China and the US are: i) the recognition by Bill Clinton on the importance of China's economic growth and; ii) the US's cooperation of science technology with China. Second, the conflict between China and the US results from the discordance of opinions on the matter of human rights and military power. Second, the conflict will inevitably arise on environmental issues around the globe including a global warming. Third, while China has yet to find a legitimate reason to agree upon these issues with the US, the US urges China of its cooperation. Lastly, Both China and the US attach great importance to the alliance with Japan. This implicates that relatively, issues involving Japan take more control in the China-US relationship, than those of Korea Peninsula.

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Evaluation on Microstructure and Mechanical Properties of Severely Deformed Pure Cu (강가공된 순수 Cu의 미세조직과 기계적 특성 평가)

  • Song, Kuk-Hyun;Son, Hyun-Taek;Kim, Dae-Keun;Kim, Han-Sol;Kim, Won-Yong
    • Korean Journal of Materials Research
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    • v.21 no.5
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    • pp.263-267
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    • 2011
  • The present study was carried out to evaluate the microstructural and mechanical properties of cross-roll rolled pure copper sheets, and the results were compared with those obtained for conventionally rolled sheets. For this work, pure copper (99.99 mass%) sheets with thickness of 5 mm were prepared as the starting material. The sheets were cold rolled to 90% thickness reduction and subsequently annealed at $400^{\circ}C$ for 30 min. Also, to analyze the grain boundary character distributions (GBCDs) on the materials, the electron back-scattered diffraction (EBSD) technique was introduced. The resulting cold-rolled and annealed sheets had considerably finer grains than the initial sheets with an average size of 100 ${\mu}M$. In particular, the average grain size became smaller by cross-roll rolling (6.5 ${\mu}M$) than by conventional rolling (9.8 ${\mu}M$). These grain refinements directly led to enhanced mechanical properties such as Vickers micro-hardness and tensile strength, and thus the values showed greater increases upon cross-roll rolling process than after conventional rolling. Furthermore, the texture development of <112>//ND in the cross-roll rolling processed material provided greater enhancement of mechanical properties relative to the case of the conventional rolling processed material. In the present study, we systematically discuss the enhancement of mechanical properties in terms of grain refinement and texture distribution developed by the different rolling processes.

Locomotive Mechanism Based on Pneumatic Actuators for the Semi-Autonomous Endoscopic System (자율주행 내시경을 위한 공압 구동방식의 이동메카니즘)

  • Kim, Byungkyu;Kim, Kyoung-Dae;Lee, Jinhee;Park, Jong-Oh;Kim, Soo-Hyun;Hong, Yeh-Sun
    • Journal of Institute of Control, Robotics and Systems
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    • v.8 no.4
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    • pp.345-350
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    • 2002
  • In recent years, as changing the habit of eating, the pathology in the colon grows up annually. The colonoscopy is generalized, but if requires much time to acquire a dexterous skill to perform an operation and the procedure is painful to the patient. biomedical and robotic researchers are developing a locomotive colonoscope that can travel safe1y in colon. In this paper, we propose a new actuator and concept of semi-autonomous colonoscope. The micro robot comprises camera and LED for diagnosis, steer- ing system to pass through the loop, pneumatic actuator and bow-shaped flexible supporters to control a contact force and to pass over haustral folds in colon. For locomotion of semi-autonomous colonoscope, we suggest an actuator that is based on impact force between a cylinder and a piston. In order to validate the concept and the performance of the actuator, we carried out the simulation of moving characteristics and the preliminary experiments in rigid pipes and on the colon of pig.

Study on Residual Stress Distribution in Thick Plate Welded Material Using Indentation Equipment (압입시험기를 이용한 후판용접재의 잔류응력 분포에 관한 연구)

  • Huh, Sun-Chul;Kim, Gwi-Nam;Lee, Jong-Seok;Park, Cheol-Hong;Park, Joun-Sung;Park, Won-Jo
    • Journal of Ocean Engineering and Technology
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    • v.25 no.6
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    • pp.66-71
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    • 2011
  • Recently, the production of shipbuilding and offshore plant industries, with a trend toward large structures, has led to an increased use of high strength ultra-thick plates. The use of ultra-thick plates increases the welding tasks, and the welding process generates distortion and residual stress in the weldment because of the rapid heating and cooling. Welding distortion and residual stress in the welded structure resulte in many troubles such as deformation and life deterioration. In particular, the welding residual stress has an important effect on welding deformation, fatigue, buckling strength, brittleness, etc. The purpose of this study was to evaluate the residual stress at a multi-pass weldment using an experimental method for EH36 high-tension steel. In this experimental method, AIS3000 was used to measure the residual stress of a welded part, HAZ, and base metal; EPMA and XRD were used to study the material properties.

Inhibitory Effects of Boesenbergia pandurata on Age-Related Periodontal Inflammation and Alveolar Bone Loss in Fischer 344 Rats

  • Kim, Haebom;Kim, Changhee;Kim, Do Un;Chung, Hee Chul;Hwang, Jae-Kwan
    • Journal of Microbiology and Biotechnology
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    • v.28 no.3
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    • pp.357-366
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    • 2018
  • Periodontitis, an infective disease caused by oral pathogens and the intrinsic aging process, results in the destruction of periodontal tissues and the loss of alveolar bone. This study investigated whether Boesenbergia pandurata extract (BPE) standardized with panduratin A exerted anti-periodontitis effects, using an aging model representative of naturally occurring periodontitis. In aged rats, the oral administration of BPE ($200mg{\cdot}kg^{-1}{\cdot}day^{-1}$) for 8 weeks significantly reduced the mRNA and protein expression of $interleukin-1{\beta}$, nuclear factor-kappa B, matrix metalloproteinase (MMP)-2, and MMP-8 in gingival tissues (p < 0.01). In alveolar bone, histological analysis with staining and micro-computed tomography revealed the attenuation of alveolar bone resorption in the BPE-treated aged group, which led to a significant reduction in the mRNA and protein expression of nuclear factor of activated T-cells c1 (NFATc1), c-Fos, tartrate-resistant acid phosphatase, and cathepsin K (p < 0.01). BPE not only increased the expression of osteoblast differentiation markers, such as alkaline phosphate, and collagen type I (COL1A1), but also increased the ratio of osteoprotegerin to RANKL. Collectively, the results strongly suggested that BPE is a natural resource for the prevention or treatment of periodontal diseases.

A Study on Improvement of Evaluation & Budget Coordination System for Effective NRDP (국가연구개발사업의 종합조정 제도개선방안에 관한 연구 -'04년도 종합조정을 중심으로-)

  • Jeong, Geun-Ha;Mun, Jin-Gyeong;Park, Mun-Su;Park, Byeong-Mu
    • Journal of Korea Technology Innovation Society
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    • v.8 no.1
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    • pp.183-208
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    • 2005
  • In recent years, national R&D programs tend to become larger and more complicated, which necessitates strengthening the overall coordination of national R&D programs at the inter-ministerial level from the program planning stage. This paper looks into the status and problems of Korea's national R&D programs and proffers ways to improve the current system It highlights the problems shown in the process of the 2004 overall coordination and their rectification. First, various ad-hoc private-led committee brought about inefficiency in decision making process. Therefore, it is necessary to streamline such committees and strengthen the function of the Office of Science and Technology Innovation, Second, in view of the implementation of the overall coordination system, it is necessary to identify the problems in full detail that were raised in the course of the previous year's overall coordination so that new projects can be allotted minimal grades and follow-up activities can be efficiently put into execution. Third, it is necessary to establish standing committees for constant review and efficient utilization that will be devoted to reviewing programs overlapped and their linkage. Fourth, priority of investment regarding the nation's strategic policy direction should be reflected. Fifth, given the lack of performance-based evaluation system, it is necessary to develop macro and micro evaluation indices in conjunction with enacting the tentatively named "Performance-based Law." The overall coordination system of national R&D programs should be supplemented and further developed in relation to the aforementioned problems and their rectification in order to enhance the expertise, fairness, and efficiency of the nation's R&D coordination system.

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Experiences of Korean-American Women with High Risk Hereditary Breast Cancer (고위험 유전성 유방암을 지닌 한국계 미국 여성의 질병경험)

  • Choi, Kyung-Sook;Jun, Myung-Hee;Anderson, Gwen
    • Asian Oncology Nursing
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    • v.12 no.2
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    • pp.175-185
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    • 2012
  • Purpose: This micro-ethnographic study aimed to understand coping experiences of Korean-American (K-A) women after diagnosis with breast cancer due to a hereditary gene mutation. Methods: Participatory observation and in-depth interviews were performed at one breast cancer screening center in Southern California, in 2005 with eleven first generation K-A immigrant women. All transcribed interviews and field notes were analyzed using ethnographic methodology. Results: K-A women's experience varied based on acculturation risk factors including: limited English speaking ability; disrupted family relationships, individualistic family values, or intergenerational communication barriers; lack of Korean speaking nurses; and Korean physicians' who lacked knowledge about hereditary breast cancer risk. These risk factors led to isolation, loneliness, lack of emotional and social support. In comparison to Korean homeland women in a similar medical situation, these K-A immigrants felt disconnected from the healthcare system, family support and social resources which increased their struggling and impeded coping during their survivorship journey. These women were not able to access self-support groups, nor the valuable resources of nurse navigator programs. Conclusion: Professional oncology associations for nurses and physicians have a moral obligation to support and promote knowledge of hereditary cancer risk and self-help groups for non-native speaking immigrants.

Buckling behavior of smart MEE-FG porous plate with various boundary conditions based on refined theory

  • Ebrahimi, Farzad;Jafari, Ali
    • Advances in materials Research
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    • v.5 no.4
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    • pp.279-298
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    • 2016
  • Present disquisition proposes an analytical solution method for exploring the buckling characteristics of porous magneto-electro-elastic functionally graded (MEE-FG) plates with various boundary conditions for the first time. Magneto electro mechanical properties of FGM plate are supposed to change through the thickness direction of plate. The rule of power-law is modified to consider influence of porosity according to two types of distribution namely even and uneven. Pores possibly occur inside FGMs due the result of technical problems that lead to creation of micro-voids in these materials. The variation of pores along the thickness direction influences the mechanical and physical properties. Four-variable tangential-exponential refined theory is employed to derive the governing equations and boundary conditions of porous FGM plate under magneto-electrical field via Hamilton's principle. An analytical solution procedure is exploited to achieve the non-dimensional buckling load of porous FG plate exposed to magneto-electrical field with various boundary condition. A parametric study is led to assess the efficacy of material graduation exponent, coefficient of porosity, porosity distribution, magnetic potential, electric voltage, boundary conditions, aspect ratio and side-to-thickness ratio on the non-dimensional buckling load of the plate made of magneto electro elastic FG materials with porosities. It is concluded that these parameters play remarkable roles on the dynamic behavior of porous MEE-FG plates. The results for simpler states are confirmed with known data in the literature. Presented numerical results can serve as benchmarks for future analyses of MEE-FG plates with porosity phases.

Evaluation of the Effect of Rotating Tool for Friction Stir Welding Al6005-T6 (회전공구 회전속도에 따른 알루미늄 합금 (Al6005-T6)의 마찰교반접합 특성 연구)

  • Choi, Dooho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.11
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    • pp.124-129
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    • 2017
  • In this study, we report characteristics of friction stir welding (FSW) technique applied to Al-6005-T6 extruded sheets, which is a common material for railway car bodies. With the welding speed fixed at 300 mm/min, the revolution per minute (RPM) of the rotating tool was varied from 600 to 1800 RPM, with the aim at evaluating the resultant microstructure and mechanical behaviors. Comparison is also made with the conventional Metal Inert Gas (MIG) welding technique. Unlike MIG, no micro-voids were observed for FSW specimens. Hardness measurement revealed that the increased heat input by increasing RPM results in widened heat affected zone (HAZ) and decreased hardness for HAZ due to grain coarsening. Hardness results for the nugget do no show difference. During tensile tests, specimens fractured at HAZ, and increasing rpm led to decrease of the yield stress and tensile stress for the selected RPM range, which is considered to be due to the grain coarsening for HAZ.